1. Field of the Invention
The invention relates to a lithium ion conducting material in which the amount of produced hydrogen sulfide is reduced by stabilizing a sulfur component before hydrogen sulfide is produced.
2. Description of the Related Art
With a rapid proliferation of information-related equipment and communication equipment, such as personal computers, camcorders and cellular phones, in recent years, it becomes important to develop a battery used as a power supply of the information-related equipment or the communication equipment. In addition, in automobile industry, or the like, development of a high-power and high-capacity battery for electric vehicles or hybrid vehicles has been proceeding. Currently, among various types of battery, a lithium battery becomes a focus of attention in terms of high energy density.
Most of currently commercially available lithium batteries employ an electrolytic solution that contains a flammable organic solvent. Therefore, a safety device, which restricts temperature rise when short circuit occurs, needs to be attached to these lithium batteries, or the structure and the material of the lithium batteries need to be improved to prevent the short circuit.
In contrast to this, all-solid lithium batteries that replace an electrolytic solution with a solid electrolyte layer do not use a flammable organic solvent in the batteries. For this reason, it is considered that the all-solid lithium batteries are excellent in manufacturing cost and productivity. Furthermore, a sulfide-based solid electrolyte material is known as a solid electrolyte material used for the solid electrolyte layer (for example, see Japanese Patent Application Publication No. 2002-109955 (JP-A-2002-109955)).
The sulfide-based solid electrolyte material has a high lithium ion conductivity, so it is useful to obtain a high-power battery. However, when the sulfide-based solid electrolyte material contacts water (including moisture; the same applies to the following description), hydrogen sulfide may be produced. Therefore, various researches have been pursued on a technique for trapping hydrogen sulfide produced. For example, Japanese Patent Application Publication No. 2008-103245 (JP-A-2008-103245) describes a sulfide-based secondary battery in which the outer peripheral portion of a cell is covered with a substance (alkaline chemical compound) that traps and detoxifies hydrogen sulfide gas. In addition, Japanese Patent Application Publication No. 2008-103283 (JP-A-2008-103283) describes an all-solid battery in which a sulfide-based all-solid battery element is covered with a sheathing material made of thermosetting resin and then the sheathing material is further covered with an adsorbent and/or an alkaline substance-containing material.
In JP-A-2008-103245 and JP-A-2008-103283, an adsorber or an alkaline substance is used to trap hydrogen sulfide; however, the adsorber or the alkaline substance originally does not inhibit production of hydrogen sulfide.
The inventors diligently studied and found that a sulfur component may be stabilized before hydrogen sulfide is produced in such a manner that an inhibitor that contains a metal element having an ionization tendency lower than that of hydrogen is used, and reached the invention.